std::mem_fn

 

C++

Idioma

Conceptos

Utilidades de la biblioteca

Strings biblioteca

Contenedores biblioteca

Algoritmos biblioteca

Los iteradores biblioteca

Numéricos biblioteca

Entrada / salida de la biblioteca

Localizaciones biblioteca

Expresiones biblioteca Regular (C++11)

Operaciones de biblioteca Atómica (C++11)

Tema Biblioteca de ayuda (C++11)

 

Utilidades de la biblioteca

Escriba apoyo (basic types, RTTI, type traits)

Gestión de memoria dinámica

Gestión de errores

Programa de servicios públicos

Funciones variadic

Fecha y hora

Objetos Function

initializer_list (C++11)

bitset

hash (C++11)

Operadores relacionales Original: Relational operators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

rel_ops::operator!= rel_ops::operator> rel_ops::operator<= rel_ops::operator>=

Pares y tuplas Original: Pairs and tuples The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

pair

tuple (C++11)

piecewise_construct_t (C++11)

piecewise_construct (C++11)

Cambiar, hacia adelante y mover Original: Swap, forward and move The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

swap

forward (C++11)

move (C++11)

move_if_noexcept (C++11)

declval (C++11)

 

Objetos Function

Envoltorios de función Original: Function wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
function (C++11)
mem_fn (C++11)
bad_function_call (C++11)
Enlazar Original: Bind The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
bind (C++11)
is_bind_expression (C++11)
is_placeholder (C++11)
_1, _2, _3, ... (C++11)
Envolturas de referencia Original: Reference wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
reference_wrapper (C++11)
ref cref (C++11) (C++11)
Envoltorios Operador Original: Operator wrappers The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
plus minus negate multiplies divides modulus logical_and logical_or logical_not	equal_to not_equal_to greater less greater_equal less_equal bit_and bit_or bit_xor
Negadores Original: Negators The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_negate binary_negate	not1 not2
Desaprobado aglutinantes y adaptadores Original: Deprecated binders and adaptors The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
unary_function (obsoleto)
binary_function (obsoleto)
ptr_fun (obsoleto)
pointer_to_unary_function (obsoleto)
pointer_to_binary_function (obsoleto)
mem_fun (obsoleto)
mem_fun_t mem_fun1_t const_mem_fun_t const_mem_fun1_t (obsoleto) (obsoleto) (obsoleto) (obsoleto)
mem_fun_ref (obsoleto)
mem_fun_ref_t mem_fun1_ref_t const_mem_fun_ref_t const_mem_fun1_ref_t (obsoleto) (obsoleto) (obsoleto) (obsoleto)
binder1st binder2nd (obsoleto) (obsoleto)
bind1st bind2nd (obsoleto) (obsoleto)

 

Defined in header <functional>
template< class R, class T > /*unspecified*/ mem_fn(R T::* pm);	(1)	(ya que C + +11)
template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...)); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) volatile); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const volatile); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) volatile &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const volatile &); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) &&); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const &&); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) volatile &&); template< class R, class T, class... Args > /*unspecified*/ mem_fn(R (T::* pm)(Args...) const volatile &&);	(2)	(c + 11, pero defecto)

std::mem_fn Función plantilla genera objetos envolventes para saber cómo dirigirse a los miembros, que puede almacenar, copiar, e invocar un puntero al miembro. Ambas referencias e indicadores (incluyendo punteros inteligentes) a un objeto se puede utilizar cuando se invoca una std::mem_fn .

Original:

Function template std::mem_fn generates wrapper objects for pointers to members, which can store, copy, and invoke a pointer to member. Both references and pointers (including smart pointers) to an object can be used when invoking a std::mem_fn.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Las sobrecargas (2) se presentan como defecto .

Original:

The overloads (2) are reported as defect.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

El resolution, que recientemente ha sido votada como "Tentativamente Ready" se propone eliminar todas las sobrecargas (2) .

Original:

The resolution, which has recently been voted "Tentatively Ready" proposes to remove all the overloads (2).

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Esto romperá algo de código, véase el ejemplo 3 .

Original:

This will break some code, see Example 3.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Parámetros

pm

-

puntero al miembro que va a ser envuelto Original: pointer to member that will be wrapped The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Valor de retorno

std::mem_fn devuelve una envoltura llamada de tipo no especificado que tiene los miembros siguientes:

Original:

std::mem_fn returns an call wrapper of unspecified type that has the following members:

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

std :: mem_fn

Original:

std::mem_fn

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Return type

Member types

tipo Original: type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	definition
result_type	el tipo de retorno de pm pm si es un puntero a función miembro, no está definido para el puntero a objeto miembro Original: the return type of pm if pm is a pointer to member function, not defined for pointer to member object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
argument_type	T*, posiblemente cv-calificado, si pm es un puntero a función miembro sin argumentos Original: T*, possibly cv-qualified, if pm is a pointer to member function taking no arguments The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
first_argument_type	T* pm si es un puntero a función miembro toma un argumento Original: T* if pm is a pointer to member function taking one argument The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
second_argument_type	T1 pm si es un puntero a función miembro toma un argumento de tipo T1 Original: T1 if pm is a pointer to member function taking one argument of type T1 The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Member function

operator()	invoca al destino de un objeto determinado, con parámetros opcionales Original: invokes the target on a specified object, with optional parameters The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (miembro público función)

Excepciones

Ninguno .

Original:

None.

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

Ejemplo 1

Utilice mem_fn para almacenar y ejecutar una función miembro y un objeto miembro:

Original:

Use mem_fn to store and execute a member function and a member object:

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <functional>
#include <iostream>
 
struct Foo {
  void display_greeting() {
    std::cout << "Hello, world.\n";
  }
  void display_number(int i) {
    std::cout << "number: " << i << '\n';
  }
  int data = 7;
};
 
int main() {
  Foo f;
 
  auto greet = std::mem_fn(&Foo::display_greeting);
  greet(f);
 
  auto print_num = std::mem_fn(&Foo::display_number);
  print_num(f, 42);
 
  auto access_data = std::mem_fn(&Foo::data);
  std::cout << "data: " << access_data(f) << '\n';
}

Output:

Hello, world.
number: 42
data: 7

Ejemplo 2

Pasar una función miembro para std::transform para crear una secuencia de números:

Original:

Pass a member function to std::transform to create a sequence of numbers:

The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.

#include <iostream>
#include <functional>
#include <iterator>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
 
int main()
{
    std::vector<std::string> words = {"This", "is", "a", "test"};
    std::vector<std::unique_ptr<std::string>> words2;
    words2.emplace_back(new std::string("another"));
    words2.emplace_back(new std::string("test"));
 
    std::vector<std::size_t> lengths;
    std::transform(words.begin(),
                   words.end(),
                   std::back_inserter(lengths),
                   std::mem_fn(&std::string::size)); // uses references to strings
    std::transform(words2.begin(),
                   words2.end(),
                   std::back_inserter(lengths),
                   std::mem_fn(&std::string::size)); // uses unique_ptr to strings
 
    std::cout << "The string lengths are ";
    for(auto n : lengths) std::cout << n << ' ';
    std::cout << '\n';
}

Output:

The string lengths are 4 2 1 4 7 4

Ejemplo 3

#include <functional>
 
struct X {
  int x;
 
        int& easy()      {return x;}
        int& get()       {return x;}
  const int& get() const {return x;}
};
 
 
int main(void)
{
    auto a = std::mem_fn        (&X::easy); // no problem at all
//  auto b = std::mem_fn<int&  >(&X::get ); // no longer works with new specification
    auto c = std::mem_fn<int&()>(&X::get ); // works with both old and new specification
    auto d = [] (X& x) {return x.get();};   // another approach to overload resolution
}

Ver también

function (C++11)	envuelve objeto que se puede llamar de cualquier tipo con la firma especificada llamada de función Original: wraps callable object of any type with specified function call signature The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (clase de plantilla)
bind (C++11)	se une uno o más argumentos a un objeto de función Original: binds one or more arguments to a function object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (función de plantilla)